Various environmental stresses, such as plant pathogenic microorganism, drought, high-concentration salt, low temperature and high temperature, act as factors that suppress the growth of plants and limit the production of crops in many important agricultural fields. It is known that Ralstonia solanacearum, one of plant pathogenic microorganism, penetrates the roots of plants and clogs the vessels so as to suppress water supply, thus withering the leaves of the host plants (Vasse et al., Mol. Plant-Microbe Interact, 8:241-251, 1995; Wallis et al, Physiol. Plant Pathol, 13:307-31, 1978). Those known to be main host plants of Ralstonia solanacearum include about 450 important crops, including tropical crops, subtropical crops and cereals, such as tomato, potato, tobacco plant, banana and olive (Hayward, Annu. Rev. Phytopathol, 29:65-87, 1991).
Also, when plants are exposed to environmental stresses, such as high-concentration salt, high temperature, low temperature and drought, osmotic imbalance and ionic imbalance in the plant cells will occur, and so the growth and photosynthesis of plants will be suppressed.
Meanwhile, plants have evolutionally developed defense mechanisms against such environmental stresses. Typical example of defense mechanisms against plant pathogenic microorganism include the synthesis of plant hormones, such as salicylic acid, jasmonic acid and ethylene, the synthesis of antibiotic compounds, such as phytoallexin, cell wall enforcement, and the expression of various pathogen resistance genes. Also, defense mechanisms against high-concentration salt stress include the maintenance of ion homeostasis by several transporters located in the plant cell membrane, and the activation of salt overly sensitive (SOS) signaling pathways having resistance to high-concentration salt stress (Zhu, J. K., Curr. Opin. Plant Biol, 6:441-445, 2003). Defense mechanisms against stresses, such as drought and low temperature, include mechanisms using ABA-dependent signaling pathways or ABA-independent signaling pathways (Zhu, J. K., Annu Rev Plant Biol, 53:247-273, 2002).
However, the above-described defense mechanisms against environmental mechanisms, which result from, e.g., pathogen resistance proteins, transporters, and various kinases, have species-specific or environment-specific characteristics, and thus have a shortcoming in that they cannot induce a broad spectrum of resistance (Bent, A. F., Plant Cell, 8:1757-1771, 1996).
Accordingly, many studies on methods capable of simultaneously expressing a group of relevant genes rather than individually expressing stress-resistant genes contained in plants themselves have been recently conducted. Among these studies, in particular, a study on transcription factors that regulate the expression of a group of environmental stress-resistant genes receives attention. For example, the effects of transcription factors CBF and Alfin1, which regulate a group of cold-resistant genes or salt-resistant genes, were verified, and an ethylene response element biding protein (EREBP) is known as a transcription factor that regulates the expression of a group of pathogen resistance genes. As another example, there are AP2 family transcription factors. The AP2 family transcription factors are classified into several groups, such as ethylene response factor (ERF), dehydration-responsive element-binding (DREB)/C-repeat (CRT)/DRE-binding factor (CBF) and RAV. ERF-type transcription factors bind to the GCC-box to regulate the expression of stress-responsive genes.